@brunodigiorgio , When you have a system that uses A+ and B-, you are dealing with equipment that uses a digital, communications system typically based on the RS-485 specifications. Sadly this is not compatible with any conventional thermostat including the Nest. You check to see if your system includes a conventional control system in addition to the digital.
AC Cooling Wizard
NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.
